1. Field of the Invention
The present invention relates generally to a substrate inspecting system and a substrate inspecting method and, more particularly, to a substrate inspecting system and a substrate inspecting method of inspecting physical/chemical characteristics of a substrate surface by use of electron beams.
2. Description of the Prior Art
As for a system for inspecting a defect in a semiconductor pattern by use of electron beams, Japanese Patent Application Laid-Open Publication No. 7-249393 discloses a method of obtaining an electron image indicating a state of the surface of the substrate, wherein an electron beam irradiating unit generates electron beams assuming a rectangular shape and irradiates the substrate defined as an inspection target with the electron beams as primary beams, secondary electrons, reflected electrons and backward scatter electrons (which will hereinafter be referred to as secondary electrons etc.) occurred from the substrate are guided and converged as secondary beams, and a mapping projection unit projects the secondary beams in enlargement on an electron detector, thereby obtaining the electron image thereof.
By irradiating the substrate with the primary beams, there might occur a local difference in terms of electric potential in surface regions on the substrate, depending on variations in configuration and material of the surface part of the substrate, i.e., the substrate surface or layers in the vicinity of the surface.
According to the method disclosed in the above Publication, the electron beams having a large area in section scan over the substrate, whereby a two-dimensional electron image of the substrate surface can be obtained. There arises a possibility from obtaining the above electron image, in which a physical characteristic and a chemical characteristic of the surface part of the substrate can be precisely quantitatively measured, and, if there exists a method of actualizing this in a tangible manner, it might be expected that a remarkable progress can be seen in an analysis of the physical/chemical characteristics of the substrate.
It is a primary object of the present invention to provide a substrate inspecting system and a substrate inspecting method which are capable of measuring precisely quantitatively physical/chemical characteristics of a substrate.
An energy which the secondary electrons etc., emitted from a substrate surface have, when traveling to a secondary optical system, depends upon an electric potential on the substrate surface. Therefore, a condition under which the secondary beams focus into an image on a detection surface, i.e., upon an MCP detector, varies depending on the energy of the secondary electrons etc., heading to the secondary optical system.
The inventors of the present patent application, with an emphasis put on this point, have discovered that there is established substantially a linear correlation between the image focusing condition of the secondary optical system and a surface potential distribution of the substrate. By utilizing this correlation, the inventors of the patent application have contrived a substrate inspecting system and a substrate inspecting method which are capable of quantitatively measuring electrical/physical characteristics of the substrate.
According to the first aspect of the present invention, there is provided;
A substrate inspecting system comprising: an electron beam irradiating device for irradiating a substrate defined as an inspection target with a primary electron beam, the irradiation of the primary electron beam causing secondary electrons and reflected electrons to generate from the substrate; an electron beam detection device for detecting an image and for outputting signals of the image, the detection device having a surface facing the substrate, the secondary electron beam being made of the secondary electrons and the reflected electrons generated from the substrate, and the image being formed by the secondary electron beam and indicating a state of surface part of the substrate; a projection device for projecting the secondary electrons and the reflected electrons as the secondary beam in enlargement on the surface of the electron beam detection device, the projection device including: an electron beam separator for separating the secondary electron beam from the primary beam, by deflecting the primary electron beam to travel to the substrate, and by allowing the secondary electron beam to travel in a direction of the electron beam detection device; and, a control device for controlling the projection device so as to have an image forming condition in accordance with a correlation between a state of the substrate and an energy of the secondary electrons and the reflected electrons, and for detecting a physical characteristic and/or a chemical characteristic of the substrate on the basis of the image signals obtained by the electron beam detection device, the energy of the secondary electrons and the reflected electrons being various depending on the state of the substrate, and the image forming condition is a condition for forming the secondary beam on the surface of the electron beam detection device.
According to the present invention, the secondary beams are controlled under such an image forming condition that the secondary beams, from a arbitrary region on the substrate, form an image in accordance with the correlation between a state of the substrate and an energy of secondary electrons and the reflection electrons because the energy varies depending on an electrical state of the substrate. Physical and/or chemical characteristics of the substrate are to be quantitatively measured based on the image signals obtained under this image forming condition. It is therefore feasible to inspect a defect in the physical and/or chemical characteristics of the substrate in the process of being manufactured in a non-contact manner. This makes it possible to promptly specify a manufacturing process with the defect.
According to the second aspect of the present invention, there is provided;
A substrate inspecting system comprising: an electron beam irradiating device for irradiating a substrate defined as an inspection target with a primary electron beam, the substrate being to be formed with an integrated circuit, the irradiation of the primary electron beam causing secondary electrons and reflected electrons to generate from the substrate; an electron beam detection device for detecting an image and for outputting signals of the image, the detection device having a surface facing the substrate, the secondary electron beam being made of the secondary electrons and the reflected electrons generated from the substrate, and the image being formed by the secondary electron beam and indicating a state of surface part of the substrate; a projection device for projecting the secondary electrons and the reflected electrons as the secondary beam in enlargement on the surface of the electron beam detection device, the projection device including: an electron beam separator for separating the secondary electron beam from the primary beam, by deflecting the primary electron beam to travel to the substrate, and by allowing the secondary electron beam to travel in a direction of the electron beam detection device; a storage device for storing design information of the integrated circuit; an image signal processing device for outputting numerical value data indicating an electrical state of the integrated circuit on the basis of signals of the image and the design information; an arithmetic device for calculating, based on the numerical value data, a threshold value serving as a criterion for judging whether or not the integrated circuit has an electrical defect; and, a control device for controlling the projection device so as to have an image forming condition in accordance with a correlation between a state of the substrate and an energy of the secondary electrons and the reflected electrons, and for detecting an electrical defect in the integrated circuit by comparing the numerical value data with the threshold value, the energy of the secondary electrons and the reflected electrons being varies depending on the electrical state of the integrated circuit, and the image forming condition is a condition for forming the secondary beam on the surface of the electron beam detection device.
The integrated circuit described above includes an insulator provided between wires (which will hereinafter be called an inter-wire insulator) in addition to the wires, and the inspection target may be either the wire within the integrated circuit or the inter-wire insulator.
According to the third aspect of the present invention, there is provided;
A substrate inspecting method comprising: a step of irradiating a substrate defined as an inspection target with a primary electron beam, the irradiating of the primary electron beam causing secondary electrons and reflected electrons to generate from the substrate; a step of deflecting the primary electron beam to travel to the substrate; a step of projecting the secondary electrons and the reflected electrons as a secondary beam in enlargement, the projecting step including a procedure for allowing the secondary electron beam to travel in a direction opposite side of the substrate; a step of detecting an image and for outputting signals of the image; the image being formed by the secondary electron beam and indicating a state of the substrate; a step of controlling the secondary electron beam under such a image forming condition that the secondary beam from an arbitrary region on the substrate forms an image in a position of detecting the secondary beam in accordance with a correlation between a state of the substrate and an energy of the secondary electrons and the reflected electrons; and, a step of detecting a physical characteristic and/or a chemical characteristic of the substrate on the basis of the image signals obtained under the image forming condition, the energy of the secondary electrons and the reflected electrons being various depending on the state of the substrate.
According to the fourth aspect of the present invention, there is provided;
A substrate inspecting method comprising: a step of irradiating a substrate formed with an integrated circuit defined as an inspection target with a primary electron beam, the irradiating of the primary electron beam causing secondary electrons and reflected electrons to generate from the substrate; a step of deflecting the primary electron beam to travel to the substrate; a step of projecting the secondary electrons and the reflected electrons as a secondary beam in enlargement, the projecting step including a procedure for allowing the secondary electron beam to travel in a direction opposite side of the substrate; a step of detecting an image and for outputting signals of the image, the image being formed by the secondary electron beam and indicating a state of the substrate; a step of controlling the secondary electron beam under such a image forming condition that the secondary beam from an arbitrary region on the substrate forms an image in a position of detecting the secondary beams in accordance with a correlation between a state of the substrate and an energy of the secondary electrons and the reflected electrons, the energy of the secondary electrons and the reflected electrons being various depending on the state of the substrate, a step of storing design information of the integrated circuit; a step of processing the image signals and outputting numerical value data which indicates an electrical state of the integrated circuit on the basis of the image signals and the design information thereof; a step of calculating, based on the numerical value data, a threshold value serving as a criterion for judging whether or not the integrated circuit is appropriately formed; and, a step of detecting an electrically defective portion in the integrated circuit by comparing the numerical value data with the threshold value.
The integrated circuit described above includes an inter-wire insulator in addition to the wires, and the inspection target may be either the wire within the integrated circuit or the inter-wire insulator.